Sistema de Combustible Con Inyector Bomba PDE y EDC S6. Descripción de Funcionamiento

03:04-09 Issue 1

en

Fuel system with unit injector PDE and EDC S6 Function Description

EDC 135 261

S6

1 714 486

 Scania CV AB 2004, Sweden

Contents

Contents Important

.................................................................................. 3

General

.................................................................................. 4 The path of the fuel................................................... 5 Fuel quantity and injection timing............................ 7

Components in the fuel system

Feed pump ................................................................ 8 Hand pump ............................................................... 9 Fuel manifold.......................................................... 10 Pressure relief valve................................................ 10 Unit injector............................................................ 11 Fuel filter ................................................................ 17

EDC

Overview ................................................................ 18 Components on the engine ..................................... 19 Components in the driver area................................ 32 Warning system ...................................................... 38 Interaction with other systems................................ 42

Important

Important! The safety precautions and warnings in the work description must be read thoroughly before any work is carried out. Using only the function description as a basis for the work is not permitted.

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3

General

General A fuel system with EDC, Electronic Diesel Control, and unit injectors PDE, Pumpe- DüseEinheit, consists – besides the fuel lines and a fuel tank – of the following parts.

found in the section EDC.

1 A feed pump 2 A hand pump 3 An electronic control unit 4 A fuel filter 5 One unit injector, of type PDE, per cylinder 6 A fuel manifold 7 a pressure relief valve The fuel system also includes an electronic control system. The control system consists of – besides the control unit – the unit injector solenoid valves, sensors and other control units, among other things. More information about the electronic control system can be

4


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The path of the fuel


Any excess fuel returns to the fuel tank via an unpressurised return line in the fuel manifold.

The feed pump 1 draws fuel from the fuel tank and presses it through the fuel filter 2 and into the fuel manifold 3. A hand pump 4 is located on the feed pump. The hand pump is used to bleed the fuel system. There is an overflow valve 5 on the fuel manifold. The pressure relief valve constantly regulates the fuel pressure. When the pressure is too high, the pressure relief valve opens, so that the excess fuel is returned to the fuel tank. The fuel rail distributes the fuel to the unit injectors in each cylinder head. The EDC control unit controls when the unit injectors are to inject the fuel into the cylinders.

5

4 2

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1

134 117

3

5


Schematic diagram of the fuel system 1

2

A

4

3

B

C

1 2 3 4 5 6

6

Feed pump Hand pump Fuel filter Cylinders Fuel tank Fuel duct for return and excess fuel

D

5

E

6

134 540

A

A Check valve B Gear pump (feed pump) C Safety valve D Overflow valve E Drain union


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Fuel quantity and injection timing

Fuel quantity and injection timing Each unit injector consists of a pump element, a solenoid valve and a nozzle. In this way, it is possible to control the fuel injection for each individual cylinder. EDC, Electronic Diesel Control, is the electronic system that controls both how much fuel each unit injector should inject into the cylinder and also when the unit injector should inject the fuel. This control of the injection means that we can optimise the combustion, which in turn leads to cleaner exhaust gases and lower fuel consumption. The EDC system described in this booklet is designated S6. The control unit is the brain of the EDC system. The control unit processes the information both from the sensors and the components that are part of the EDC system and also from the control units in other systems. When the control unit has processed the information, it then transmits signals to the unit injectors. The signals control the injection of the fuel. The EDC system makes possible such functions as cruise control, hand throttle, speed limiter, smoke limiter and a special cold start programme.

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7


Components in the fuel system Feed pump The gear-type feed pump is positioned on the rear end of the air compressor and is driven by the crankshaft of the compressor. Its capacity is adjusted to deliver the right pressure and flow rate to all unit injectors.

134 590

The hole drilled in the flange of the feed pump is used to indicate leaks.

Feed pump location

8


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Hand pump

134 588

The hand pump is positioned on the rear end of the feed pump and is used for bleeding the fuel system. On buses, the hand pump is positioned so that it is easily accessible through the rear engine compartment door.

Location of the hand pump on the feed pump on trucks.

Location of the hand pump on buses.

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9


Fuel manifold The fuel manifold distributes the fuel into the unit injectors for each cylinder head. The fuel manifold is fastened with banjo screws that are connected to the return line to the fuel tank.

Pressure relief valve The pressure relief valve is positioned on the fuel manifold.

134 162

The pressure relief valve controls the supply pressure in the fuel system.

Pressure relief valve location on trucks

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Unit injector General There is one unit injector for each cylinder. The unit injector is positioned in the centre of the cylinder head between the four valves. The unit injector is a pump element forming a single unit with the injector nozzle. It is driven by the engine camshaft. The drive is transferred from the camshaft via a roller tappet, pushrod and rocker arm to the unit injector. Any excess fuel remaining in the unit injector after combustion returns to the fuel tank via the excess fuel duct (A). A fuel duct passes through the valve housing which has a constant flow of fuel. The fuel that flows through the unit injector operates like coolant in the unit injector. The heated fuel returns to the fuel tank via the fuel duct for return fuel (B).

1 Pump section 2 Injector section 3 Valve housing A Excess fuel duct B Fuel duct for return fuel

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The unit injector consists of three main parts. •

Pump section, containing cylinder and plunger, corresponding to the pump element in an injection pump.

•

Injector section, with nozzle sleeve, nozzle needle and spring.

•

Valve housing, with an electromagnetically controlled fuel valve.

The lower part of the unit injector is fitted in a steel sleeve with copper washer resting against the bottom of the cylinder head, similar to an ordinary injector. The upper part of the unit injector, with compression spring and valve housing, is located above the cylinder head. Injection timing and the amount of fuel to be injected are determined by the control unit. The control unit controls the electromagnetic fuel valve in the unit injector valve housing. The opening duration of the injector (injector timing) determines the amount of fuel that is injected into the cylinder. Any excess fuel from the unit injector flows to the fuel manifold via the duct in the cylinder head. The fuel then runs into the return duct in the fuel manifold via a banjo union in the overflow valve and back to the fuel tank.

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Filling phase During the filling phase, pump plunger 2 moves up to its highest position. The highest point of the cam on the camshaft has passed and the roller tappet is moving towards the camshaft base circle. Fuel valve 1 is in the open position and fuel can flow into the barrel from fuel duct 3. Filling continues until the pump plunger reaches its highest position.

1 2

4

134 141

3

1 2 3 4

Fuel valve Pump plunger Fuel duct, inlet Fuel duct, outlet

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13


Spill phase The spill phase begins when the camshaft has moved on to the position in which the cam on the camshaft starts to press pump plunger 2 down by means of the roller tappet, pushrod and rocker arm. The fuel can now flow through fuel valve 1, through the hole in the unit injector and out through fuel duct 4. The spill phase continues as long as fuel valve 1 remains open.

1 2

4

134 142

3

1 2 3 4

14



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Injection phase The injection phase begins when fuel valve 1 closes. The fuel valve closes when voltage is applied to the solenoid valve. The cam on the camshaft continues to press pump plunger 2 down by means of the rocker arm and injection takes place since the passage through the fuel valve is closed. The injection phase continues as long as fuel valve 1 remains closed.

1 2

4

134 143

3

1 2 3 4


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15


Pressure reduction phase Injection stops when fuel valve 1 opens and the pressure in the unit injector drops below the nozzle's opening pressure. The fuel flows through the open fuel valve 1, the hole in the unit injector and out through fuel duct 4. It is the closed or open position of the fuel valve which determines when injection should begin and end. The length of time the fuel valve remains closed determines the amount of fuel that is injected during each pump stroke.

1 2

4

134 144

3

1 2 3 4

16



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Fuel filter

134 587

The fuel filter is an insert filter with one filter element. The filter element is secured to the lid and when the filter is removed, the filter housing drains automatically.

Fuel filter location

In and outlets of the fuel filter on trucks 1 Bleeder nipple 2 Intake 3 Outlet 4 Return to fuel tank 5 Return from fuel manifold

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In and outlets of the fuel filter on buses 1 Bleeder nipple 2 Intake 3 Outlet 4 Bleeder nipple (used when the fuel tank is too high for the other bleeder nipple to be used.)


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Overview

EDC S6 Overview The figure below illustrates the components and systems with which the EDC control unit communicates. Communication with certain components takes place via the coordinator.

1

2

4

3

PDE

9

8

7

1 Two engine speed sensors 2 Charge air pressure and temperature sensor 3 Coolant temperature sensor 4 Oil pressure sensor 5 Unit injector solenoid valves, one per cylinder. 6 Coordinator that connects the EDC control unit to the components in the driver area.

18

134 253

5

6

7 Control unit for Opticruise 8 Control unit for Retarder 9 Control unit for ABS/TC and EBS


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Components on the engine

Components on the engine Engine speed sensors, T74 and T75

Both engine speed sensor 1 and engine speed sensor 2 read the position of the flywheel. This means that the system cannot determine which of two possible revolutions the engine is at, i.e. whether cylinder 1 or cylinder 6 is at the ignition position for example. Every time the engine is stopped and the voltage cut off, the engine position is stored. Next time the voltage is switched on, the stored position of the engine is used to determine which revolution the engine is at. When the engine has started, a system check is performed to verify that the stored position is correct.

T75

T74

134 591

There are two engine speed sensors in the EDC system, engine speed sensor 1 and engine speed sensor 2. The sensors are inductive. This means that they only produce signals when the engine is running. The signal strength varies significantly, depending on the air gap between the sensors and the flywheel as well as on the engine speed. The EDC system performs an assessment of the signal strength at different engine speeds. If the signal strength becomes too low, a fault code is generated.

1 Engine speed sensor 1, T74 2 Engine speed sensor 2, T75

Engine speed sensor location. The detail shows some of the holes in the flywheel that are detected by the engine speed sensors.

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19


The EDC control unit receives signals from both engine speed sensors. If the control unit receives a faulty signal or no signal at all from either of the engine speed sensors, the engine torque is limited for safety reasons. If the control unit receives a correct signal, the engine will behave normally again. If the control unit receives a faulty signal or no signal at all from both engine speed sensors, the engine cannot be started. If the engine is running, it will be turned off.

The interval between two of the holes is greater than the intervals between the remaining holes. When the control unit senses that this larger interval passes the sensor, it knows that the flywheel is in a specific position in relation to top dead centre (TDC UP). If the control unit detects any faults, one or more fault codes are generated.

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T 74

E44

T 75 n

n 1

2

1

2

1

2

1

2

A5

A6

118 080

The engine speed sensors detect the holes in the flywheel when the flywheel rotates and send pulses to the control unit for each hole. This allows the control unit to calculate where in the operating cycle the engine is. The control unit senses and compares the engine speed at combustion in each cylinder. The control unit seeks to keep the acceleration from each cylinder constant by adjusting the fuel volume individually for each cylinder.

Engine speed sensor connections to EDC control unit E44.


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Charge air pressure and temperature sensors, T47 The sensors for charge air pressure and temperature are integrated into one single component. Both sensors are described in more detail on the next page.

134 567

T47

Sensor location

T 47

E44

1

2

3

4

1

3

2

4

A10

118 081

P/

Sensor connection to EDC control unit E44.

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21


Charge air pressure sensor The charge air pressure sensor detects the absolute pressure in the intake manifold, i.e. the atmospheric pressure plus the positive pressure provided by the turbocharger.

The engine will then react more slowly than normal when actuating the throttle in cold weather, as the EDC control unit thinks that the air is warmer than it really is.

The EDC control unit uses the signal from the sensor to limit the fuel volume when the charge air pressure is under a certain level. The lower the pressure, the less fuel the control unit allows to go out to the unit injectors. In this way black smoke is avoided. The control unit reads the voltage from the sensor. The signal voltage is directly proportional to the charge air pressure. A high pressure gives a high voltage and vice versa. Depending on factors such as throttle actuation, engine speed, engine acceleration and charge air temperature, the control unit will expect a certain value for the charge air pressure. The deviation between the current charge air pressure and the pressure expected by the control unit can be read off using Scania Diagnos. If there are any faults in the signal, a fault code is generated. The control unit will then operate according to a pre-programmed pressure value. As a safety precaution, the engine torque is then limited. Charge air temperature sensor The charge air temperature sensor detects the temperature in the intake manifold. The EDC control unit uses the signal from the sensor to finely adjust the fuel quantity so that black smoke is not produced. The warmer the charge air, the less fuel the control unit allows to go out to the unit injectors. The sensor is of the NTC type, which means that its resistance is temperature dependent. If the temperature increases, the resistance in the sensor drops. If the voltage is outside a certain range, the control unit will operate according to a preprogrammed temperature value, and a fault code will be generated at the same time.

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Coolant temperature sensor, T33 The coolant temperature sensor affects the fuel volume and injection timing when starting the engine and when the engine is cold. It also affects the engine idling speed and maximum engine speed when the engine is cold and the engine power when it is too warm.

Directly after a cold start, the engine speed is limited to 1000 rpm in order to protect the engine, the engine idling speed is raised to 600 rpm.

T33

134 166

If the coolant temperature sensor senses that the engine is cold when attempting to start (cold start), the following will occur. If the engine does not start within 2 seconds, the fuel quantity injected will successively increase until the engine starts.

Coolant temperature sensor location

The length of time engine speed limitation is engaged varies depending on the coolant temperature: Below +10°C Above +20°C

30 seconds 3 seconds

The engine idling speed returns to normal when the coolant has reached 20 - 60°C (the temperature limit differs between engine types).

E44

1

2

1

2

A7

118 082

T 33

Coolant temperature sensor connections to EDC control unit E44.

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23


o

In certain engines, the engine power is limited when the coolant temperature exceeds 104°C. Refer to diagram. The engine power is limited so that the engine does not overheat, and a fault code is generated at the same time.

/o

100

The control unit reads the voltage from the sensor. If the voltage is outside a certain range, the control unit will operate according to a preprogrammed temperature value.

o

The engine will then have poorer cold-start characteristics and will emit more white smoke in cold weather.

24


106

118 488

C

104

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Oil pressure sensor, T5 The oil pressure sensor registers the pressure of the engine oil.

The EDC control unit expects a certain oil pressure depending on the engine speed. Below 1000 rpm, the oil pressure should be at a certain level. Over 1000 rpm the oil pressure should be at a higher level, in order to provide sufficient oil pressure for piston cooling, etc. If the oil pressure is below the permitted value, the oil pressure lamp comes on. The oil pressure lamp therefore lights at different pressure levels depending on the engine speed.

T5

134 167

The EDC control unit reads the voltage from the sensor. If the signal voltage is outside a certain range, the oil pressure sensor on the instrument panel will show 0 bar, regardless of engine speed, and a fault code will be generated at the same time.

Oil pressure sensor location

T5 P/

2

3

2

4

3

A9

4

118 083

E44

1

Oil pressure sensor connection to EDC control unit E44.

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25


EDC control unit, E44 The EDC control unit collects information which is processed into signals that control the fuel volume and injection timing solenoid valves.

The control unit converts the system voltage to a lower voltage of approximately 5 V, which it supplies to sensors, etc. These sensors are always earthed through the control unit. The control unit can be configured using Scania Programmer. For example, a maximum speed can be set up.

E44

134 585

We know that the electrical system of the vehicle has a system voltage of +24 V and is earthed via the chassis.

Engine control unit location

Every time the control unit is configured, the date and VCI identification number are stored in the memory of the control unit. This is the equivalent of security sealing.

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Sensor group

Coolant temperature sensor, T33, charge air pressure sensor, T47 and charge air temperature sensor T47 form one sensor group. This means that the voltage supply from the control unit is common to both sensors. If, for example, one sensor is short-circuited it may also affect the other.

The sensor group includes:

T33

•

Coolant temperature sensor, T33

•

Charge air pressure sensor, T47

•

Charge air temperature sensor, T47

T47 P

1

4

1

1

4

1

A7

A10

134 118

E44

Power supply to sensors

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EDC control unit, connections A

B

5

4

3

2

1

10

9

8

7

6

5

4

3

2

1

10

9

8

7

6

4 6 8

2

1

2

1

2

1

2

1

5

4

3

2

1

5

4

3

2

1

1

2 3

4

5

6

7

8

5

4

3

2

1

10

9

8

7

6

5

4

3

2

1

10

9

8

7

6

1

2 3

2

1

2

1

2

1

2

1

5

4

3

2

1

5

4

3

2

1

5 7 9

9

10

134 147

10

The EDC control unit is connected to the other EDC systems in the vehicle via connectors A and B. See illustration.

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How the pins are connected is shown below. Connectors

Pin

A1

1

Power supply, +24 V to the solenoid valve for cylinder 2, (V16).

A1

2


A1

3

Not used.

A1

4

Not used.

A1

5

Not used.

A1

6

Earthing of the solenoid valve for cylinder 2, (V16).

A1

7


A1

8

Not used.

A1

9

Not used.

A1

10

Not used.

A2

1-10

Not used.

A3

1-2

Not used.

A4

1-2

Not used.

A5

1

Input signal from engine speed sensor 1, (T74).

A5

2


A6

1


A6

2


A7

1

Input signal from the coolant temperature sensor, (T33).

A7

2

Earth for coolant temperature sensor, (T33).

A8

1-2

Not used.

A9

1

Not used.

A9

2

Voltage supply, +5 V to the oil pressure sensor, (T5).

A9

3

Input signal from the oil pressure sensor, (T5). The control unit detects the voltage level between pins 3 and 4.

A9

4

Earth for oil pressure sensor, (T5).

A9

5

Not used.

A10

1

Supply voltage, +5V to the charge air pressure and temperature sensor, (T47).

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29


30

Connectors

Pin

A10

2

Input signal from the charge air pressure sensor, (T47). The control unit detects the voltage level between pins 2 and 3.

A10

3

Earthing of charge air pressure and temperature sensor, (T47).

A10

4

Input signal from the charge air temperature sensor, (T47). The control unit detects the voltage level between pins 3 and 4.

A10

5

Not used.

B1

1

Voltage supply, +24 V to the control unit.

B1

2

Earth connection for the control unit to chassis.

B1

3

Input signal +24 V from the starter lock (when the key is in the drive position).

B1

4

Not used.

B1

5

Not used.

B1

6

Voltage supply, +24 V to the control unit.

B1

7

Earth connection for the control unit to chassis.

B1

8

Not used.

B1

9

CAN communication, H lead

B1

10

CAN communication, L lead

B2

1


B2

2


B2

3

Not used.

B2

4


B2

5

Not used.

B2

6


B2

7


B2

8

Not used.

B2

9

Earthing of the solenoid valve for cylinder 3,(V15).

B2

10

Not used.

B3

1-2

Not used.

B4

1-2

Not used.


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Connectors

Pin

B5

1-2

Not used.

B6

1-2

Not used.

B7

1-2

Not used.

B8

1-2

Not used.

B9

1-5

Not used.

B10

1-5

Not used.

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Components in the driver area

Components in the driver area The components in the driver area belong to the coordinator. The EDC control unit will then only receive a CAN message about the status of the component. The components are described in the function description for the coordinator. Below is a short description of how the EDC control unit uses the information from the coordinator.

Accelerator pedal sensor The EDC control unit receives a CAN message from the coordinator about the position of the accelerator pedal. The EDC control unit uses the information to control the fuel volume and injection timing solenoid valves.

Control for cruise control S51 The EDC control unit receives a CAN message from the coordinator about the cruise control settings. The EDC control unit interprets the information as a desired vehicle speed or a desired engine speed and then regulates the vehicle speed or engine speed.

Brake pedal switches The EDC control unit receives a CAN message from the coordinator about the status of the brake pedal switches. The control unit uses the information to control certain functions, e.g. Cruise control.

Clutch pedal switch The EDC control unit receives a CAN message from the coordinator about the status of the clutch pedal switches. The control unit uses the information to control certain functions, e.g. Cruise control.

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Tachograph O4 The EDC control unit receives a CAN message from the coordinator about the vehicle speed. Vehicle speed sensing is a pre-condition for certain functions, e.g. Cruise control and Speed limitation. If the EDC control unit does not have any information on the vehicle speed, it operates according to the pre-programmed speed of 15 km/h.

Warning lamp for EDC, W27 The EDC control unit sends information to the coordinator about whether the indicator lamp should be lit or not. The indicator lamp lights for a few seconds when the ignition is switched on to ensure that it works. When the engine is switched off, the indicator lamp comes on while the EDC control unit carries out a functional check of the EDC system. When the check is complete, the lamp goes out. When the engine is running, the warning lamp should normally be off. If there is a fault in the EDC system, the warning lamp comes on. If the indicator lamp flashes continuously and the vehicle cannot be started, a serious fault has occurred in the control unit. It will then be impossible to establish contact with the control unit. The control unit must be renewed.

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33


Cruise control Cruise control Note: Set the switch to the OFF position when the cruise control is not in use. In the ON position the cruise control may be engaged by mistake.

ON OFF ACC RET RES

Engaged Disengaged Accelerate Decelerate (reduce vehicle speed) Resume selected speed

03_0767

Below is a description of the cruise control functions.

Connection The road speed must be at least 20 - 35 km/h (the speed limit varies between engine types) for cruise control to be used. 1 Set the switch to ON. 2 Drive at the desired road speed. Press ACC or RET to engage the cruise control and then release the accelerator pedal. Setting the road speed Alter the set road speed using ACC or RET. Release ACC/RET when the desired road speed is attained. Pressing and releasing once alters the road speed by 1 km/h.

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Deactivation The cruise control is disengaged by activating one of the following: •

Retarder or exhaust brake

•

The cruise control switch. Press it gently towards OFF (the spring-loaded position).

•

Brake pedal

•

Clutch pedal

•

Accelerator pedal - greater vehicle speed than the set value for at least 30 seconds

Resuming the set speed After braking for example, it is easy to quickly select the previous road speed by pressing RES. The previously set value is stored until the engine is switched off or a new value is selected.

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35


Hand throttle

If the vehicle is to be driven, a gear must be engaged and the clutch pedal released before the hand throttle can be used.

03_0767

The hand throttle is used to set the desired engine speed, e.g when operating a crane. It is set via the cruise control. The hand throttle can be used in stationary vehicles and when driving at low speed, maximum 10 km/h.

Connection 1 Put the cruise control switch in the ON position. 2 Press RES, the engine will maintain the previously selected engine speed. 3 Press ACC or RET to select a new engine speed. 4 Then press RES for at least three seconds to store the engine speed. The engine speed remains stored until a new value is set, even when the engine is switched off. Switching over to idling speed •

Press OFF or

•

depress the brake or clutch pedal or

•

36

activate the exhaust brake or the retarder.


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Idling speed adjustment The engine idling speed can be adjusted between 500 and 700 rpm. It is adjusted via the cruise control. Generally speaking, the idling speed should be the lowest speed at which the engine runs smoothly. When adjusting it, the brake pedal must be depressed and the engine should be warmed up (coolant temperature more than +40°C). 1 Run the engine until it reaches normal operating temperature. 2 Put the cruise control switch in the ON position. 3 Depress the brake pedal and keep it depressed until the engine speed is set. 4 Press RES for at least three seconds. This will set the basic setting 500 rpm 5 Adjust the desired idling speed by pressing ACC or RET. Every press corresponds to 10 rpm. 6 Press RES for at least three seconds. The engine speed is now set. 7 The brake pedal can now be released. The idling speed remains stored until a new value is set, even when the engine is switched off.

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37

Warning system

Warning system General If a fault occurs in the EDC system, one or more of the following measures will be carried out by the EDC control unit, depending on what the fault is. •

The warning lamp for EDC comes on. It will often go out on its own when the fault ceases. However, certain faults require the ignition to be switched off and on, or the engine to be stopped and restarted, for it to go out.

•

Functions like cruise control and hand throttle are disengaged.

•

Torque is limited.

•

When idling, the engine runs at a slightly higher engine speed than normal.

•

The engine is switched off.

•

The engine will be forced to idle.

2

EDC 106 448

1

Warning lamp for EDC, truck

The control unit carries out the above measures in order to prevent the fault causing expensive damage and at worst leading to uncontrolled throttle actuation. If the engine is not turned off, the vehicle can often be driven to a workshop. It should be remembered, however, that the system has less than normal safety margins, especially if engine output is reduced.

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Warning system

Shutdown test Every time the engine is switched off, the EDC control unit carries out a special test of the EDC system. While this shutdown test is running, the warning lamp is lit. When the check is complete, the following occurs: The control unit switches off and the lamp goes out. The control unit receives battery voltage all the time. If the control unit discovers a fault during the shutdown test, the warning lamp will come on the next time the engine is started, even if the fault is no longer present. The control unit must carry out a fault-free shutdown test before the warning lamp goes out.

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39

Warning system

Fault codes When the control unit discovers a fault, or something which it interprets as abnormal, it generates a fault code. The warning system can generate approx. 125 different fault codes. One flashing code in EDC S6 corresponds to several different fault codes.

Arrangement of flashing codes

A single very long flash of 4 seconds indicates that no fault codes are stored in the memory.

40


106 158

The example to the right symbolises flashing code 25.

106 157

The flashing codes which are flashed out by the diagnostics lamp are arranged in a certain way. The long flashes -1 second - shown first represent tens. The shorter flashes - 0.3 seconds - that follow represent units.

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Warning system

Fault code memory

Limp-home mode

The EDC control unit memory has sufficient capacity to store a maximum of 40 fault codes.

If the accelerator pedal sensor potentiometer fails, a fault code will be generated in the coordinator. A fault code will also be generated in the EDC control unit to report that there is a fault in the coordinator. The vehicle can, however, be driven to the nearest workshop in limp-home mode. Limp-home mode is activated by releasing the accelerator pedal once so that the EDC control unit is aware that the throttle actuation switch works.

The fault codes are stored in two different places in the control unit. Erasing with the diagnostic switch erases the fault codes that are flashed on the diagnostic lamp. However, the fault codes will remain stored in another memory that can only be accessed using Scania Diagnos. Scania Diagnos can be used to see how many times each fault has occurred; this information can be valuable with a loose connection for example. Scania Diagnos is used to erase both fault code memories at the same time.

When the accelerator pedal is then depressed the throttle actuation switch is closed. The closed throttle actuation switch gives a throttle actuation equal to half of full throttle. When the accelerator pedal is released, the engine will run at idling speed. If the idling switch is faulty the engine will run at 750 rpm.

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41

Interaction with other systems


ABS/TC and EBS

Opticruise

The ABS/TC system influences the EDC system and vice versa.

Opticruise influences the EDC system and vice versa.

The ABS/TC control unit continuously senses if one of the driving wheels is spinning. TC engine control is activated when the driving wheels spin and the throttle actuation is then reduced, irrespective of the accelerator pedal position, until they cease to spin.

The Opticruise control unit continuously receives information from the EDC control unit about data such as engine speed or accelerator pedal position. The EDC control unit receives a CAN message from the coordinator about the position of the accelerator pedal.

The EDC control unit receives a CAN message from the coordinator about the position of the accelerator pedal. The EDC control unit forwards information about the accelerator pedal position to the ABS/TC control unit.

During gear changing, the Opticruise control unit takes control of the EDC system and controls throttle actuation.

The EBS and ABS/TC control units communicate with the EDC control unit in the same way.

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Exhaust brake

Retarder

The exhaust brake influences the EDC system, but not vice versa.

The retarder influences the EDC system and vice versa.

When the exhaust brake is activated, a message is sent to the EDC control unit, which then deactivates the cruise control.

When the retarder is activated, a message is sent to the EDC control unit, which then deactivates the cruise control.

When the exhaust brake is activated via the brake pedal, the fuel supply is switched off.

If the accelerator pedal is depressed while the retarder is activated, the retarder will immediately be deactivated and the vehicle will respond to the accelerator pedal.

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PWM signals Note: A PWM signal cannot be reliably measured using an ordinary multimeter. Instead, use the fault codes to locate the cause of any possible malfunctions.

U

PWM means that a signal is Pulse Width Modulated. The PWM signal is a square wave with a constant frequency (T). The voltage level (U) is also constant; the variable is the activation time calculated as a percentage of each cycle (the cycle is shown as 100% in the illustrations). The PWM signal transmits very accurate information.

T

106 159

10% 100%

U

T

100%

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106 160

90%

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CAN communication Note: Bodywork builders and coachbuilders must not connect their own systems to the CAN network without the approval of Scania. If any other equipment other than the factory fitted equipment is connected, safety and reliability can be affected.

circuit - in a special memory. This memory may be compared to a number of radio receivers that are all on but set to different radio stations to listen to several radio programmes simultaneously. In this way, the control unit continuously senses what is happening.

Note: It is not possible to measure or check CAN messages with a multimeter either. Use the fault codes to locate the cause of any possible malfunctions. CAN is an abbreviation of Controller Area Network. CAN communication is used to reduce the number of cables in the vehicle and at the same time increase reliability. The communication circuit consists of two cables, CAN H (High) and CAN L (Low). OPTICRUISE ABS/TC

EDC

EBS

116 757

COO

Several different systems are connected to these two cables and in this way form a network. CAN communication is used for example between EDC, ABS/TC, EBS, the retarder, Opticruise and the coordinator. In simple terms, CAN communication is rather like radio. The data messages that travel along a CAN cable can be compared to radio waves that travel through the air. When listening to the radio, the receiver is set so that one radio station is heard at one time. Only one station is heard, even though many other radio stations are transmitting simultaneously. A control unit does approximately the same with the messages that travel through a CAN cable. It listens, for example, for information from the EDC control unit concerning the coolant temperature, receives this value and uses it in its calculations. The control unit receives several CAN messages - which are sent through the communications

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Sistema de Combustible Con Inyector Bomba PDE y EDC S6. Descripción de Funcionamiento

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